A while ago I got a text from a client, someone I’ve trained on and off over the past couple years.

“I’m coming back Monday if u have time. 4 or 5 days a week. We r on a mission. Cruise in 8 weeks. Gotta flatten this belly.”

I got a familiar warning in my gut not to block out a lot of time for her, because we’d been through this before. She has what I call All or Nothing Syndrome, and it’s very common. She’s either all about her fitness and diet – 100 percent spot-on, perfect in every aspect of her regimen – or she most definitely is not.

Maybe you know someone like this. Before they (re)start their new fitness program, they create an aggressive slate of workouts and meal plans. They buy pricey supplements and maybe some new workout clothes. The pantry gets cleaned out. They eat a few last-hurrah meals, and when the appointed day dawns, they approach their program with ferocity.

All of that is good stuff (well, except perhaps the big pre-launch food splurges). Pretty much everyone needs to schedule time for intentional exercise and we all should pay attention to the quality and quantity of the food we eat. But sometimes, we set the bar so high that it can never be reached.

On Monday my client showed up, eager for her first session. We talked a lot about diet – what was the perfect protein powder? Should she eat eggs or oatmeal for breakfast? Maybe she should visit the health food store and go totally organic. She was planning to do extra cardio at night by playing Wii with the kids or, when the weather allowed, running with the dog.

As a trainer, I was kind of stuck – I didn’t want to discourage her, but I did caution about pushing for too much too soon.

On day three, she was running late. She had to answer the phone twice during our session. Day four, I got a last-minute text telling me her child needed to be dropped off at the grandmother’s and she wouldn’t make the session.

The next week she made it to the gym twice. She was stressed from work, she said. And then I didn’t see her again. But I will in a few months, and I hope so, because I like her and believe that one day, things will click and she’ll find a way to integrate healthier habits into her life.

The problem with all-or-nothing thinking is that either you’re all – or you’re nothing.

It’s challenging to stick with a demanding diet or workout plan,, even without the responsibilities of everyday life – job, home, spouse, kids, etc. Having to work late one day can mean you miss a workout. It happens to all of us, even to me, even though I typically spend all my waking hours at the gym because this is my career.

But if you’ve been pressuring yourself to be perfect, it won’t be long till you decide you’re weak or that your life/family/job/whatever is conspiring to keep you out of shape. And then, you give up.

It isn’t your life that’s doing the conspiring – it’s you and your thoughts. Getting to the gym twice in a week wasn’t a failure for my client, but that’s how she saw it, and so she quit.

You need to be flexible, especially at the beginning of a lifestyle change. Yes, it’s important to make a plan and do your best to stick with it. But if (when?) you falter, let your missteps help you create an even better plan that suits your real life, not the barrier-free life you imagined when you first dreamed up the plan.

For instance, if you find it impossible to exercise after work because of an erratic schedule, shift your workouts to earlier in the day. Suffering from mid-afternoon munchies? Find something healthier to eat, or try a cup of green tea and see if that helps quell the hunger.

And remember: when it comes to fitness, “something” trumps nothing, every time.